Download Diapositiva 1

1. Animals are heterotrophic by ingestion.
2. Unlike fungi that use external digestion,
animals usually digest food in a central cavity.
3. Animals produce heterogametes (eggs and
sperm) and have a diplontic life cycle; adults are
diploid.
1. Types of Symmetry
2. Germ layers refer to the number of layers
of tissues.
3. Body Cavities Are Different
.
3. They mostly live in coastal waters but there
are oceanic jellyfish and freshwater hydras.
1. 13,000 species of flatworms belong to phylum
Platyhelminthes.
2. Classification
a. Planaria and relatives are freshwater animals in
the class Turbellaria.
b. Flukes are external or internal parasites in the
class Trematoda.
c. Tapeworms are internal parasites in the class
Cestoda.
3. In addition to endoderm and ectoderm, a
mesoderm layer gives rise to muscles and reproductive
organs.
1. Turbellaria include freshwater planaria such
as Dugesia.
2. Planaria live in lakes, ponds, and streams
and feed on small living or dead organisms.
3. The head is arrow-shaped; side extensions
(auricles) are sensory organs to detect food and
enemies.
4. Two light-sensitive eyespots have
pigmentation that makes them look cross-eyed.
1. As parasites, flukes and tapeworms have
characteristic modifications.
a. Loss of predation led to loss of
cephalization; a head carries hooks and suckers to
attach to a host.
b. There is extensive development of
reproductive system with loss of other systems.
c. Well-developed nervous and
gastrovascular systems are not needed; it does not
seek out or digest prey.
1. The class Trematoda includes flukes.
2. Blood, liver, and lung flukes inhabit those
organs.
3. Fluke bodies are generally oval and elongate.
4. At the "head" an oral is sucker surrounded by
sensory papillae; another sucker helps attach.
1. A tapeworm scolex contains hooks and
suckers for attachment to intestinal wall of host.
2. Behind the head is a short neck and then a
long string of proglottids.
3. Each proglottid segment contains a full set of
both male and female sex organs and little else.
4. There are excretory canals but no digestive
system and only rudiments of nerves.
5. After fertilization, proglottids become a bag of
eggs; mature proglottids break off and pass out with
feces.
6. If eggs of tapeworms are ingested by pigs or
cattle, larvae become encysted in the muscle of
hosts.
7. The covering of ingested eggs is digested
away and larvae burrow through intestinal wall and
travel by bloodstream to lodge and encyst in muscle.
8. A cyst is a hard-walled structure sheltering a
larval worm.
9. If humans eat meat of infected pigs or cattle
and fail to cook it properly, they too become infected.
1. Pseudocoelom is a body cavity that is
incompletely lined with mesoderm; support is
provided by hydrostatic pressure of fluid in the
pseudocoelom against a tough cuticle.
2. Perhaps 500,000 species of roundworms
are in phylum Nematoda.
3. These worms are unsegmented, with a
smooth outside wall.
A. Over 110,000 living species of mollusks
belong to the phylum Mollusca
1. Mollusks have a three-part body plan: a
visceral mass, a mantle, and a foot.
2. Most are marine, but some are freshwater and
terrestrial.
3. Visceral mass contains internal organs:
digestive tract, paired kidneys, and reproductive organs.
4. Mantle covering partly surrounds visceral mass;
may secrete a shell, help develop gills or lungs.
1. Class Bivalvia contains bivalves (clams,
oysters, mussels, scallops).
2. "Bivalves" are two-part shells that are
hinged and close by powerful muscles.
3. They have no head, no radula, and little
cephalization.
4. Clams burrow with a hatchet-shaped foot;
mussels use it to produce threads to attach to
objects.
1. Class Cephalopoda ("head-footed")
includes squids, cuttlefish, octopuses, and
nautiluses.
2. Squids and octopuses squeeze water out of
the mantle cavity; water forced out through a funnel
propels them by jet propulsion.
3. Around the head are tentacles with suckers
or adhesive secretions adapted for grasping prey.
4. A head equipped with a powerful beak can
tear prey apart.
1. Class Gastropoda includes snails, land
slugs, whelks, conchs, periwinkles, sea hares,
and sea slugs.
2. Most are marine; some are freshwater or
terrestrial.
3. Herbivores use a radula to scrape food from
surfaces; carnivorous gastropods use the radula to
bore through a surface, such as a bivalve shell, to
obtain food.
4. A developed head with eyes and tentacles
projects from a coiled shell that protects visceral
mass.
1. About 12,000 species of segmented worms
are in phylum Annelida.
2. Segmentation shows by rings that circle the
body; septa partition the coelom.
3. A well-developed, fluid-filled coelom and
tough integument act as a hydrostatic skeleton.
4. Segmentation may have evolved in
conjunction with a hydrostatic skeleton.
1. Most polychaetes, marine worms, (class
Polychaeta) are marine.
2. Polychaetes possess parapodia and setae.
a. Parapodia are paddle-like appendages
used in swimming and for respiration.
b. Setae are bristles, attached to parapodia,
that help anchor polychaetes or help them move.
3. Clam worms such as Nereis are active
predators.
4. Many have well-developed cephalization;
head has well-developed jaws, eyes and other
sense organs.
5. Sedentary filter feeders possess tentacles
with cilia to create water currents and select food
particles.
6. Only during breeding do polychaetes have
reproductive organs.
7. Marine worm zygotes develop larva similar
to those of marine clams; this shows relatedness.
1. Class Oligochaeta includes earthworms with few
setae, protruding in clusters directly from body.
2. Earthworms lack both a well-developed head and
any parapodia.
3. Locomotion requires coordinated movement of body
muscles and help of setae.
a. As longitudinal muscles contract, segments bulge
and setae protrude to anchor into soil.
b. When circular muscles contract, a worm
lengthens, setae are withdrawn and the segment can be
pulled forward.
1. Leeches belong to the class Hirudinea.
2. Most are fresh water species but a few are
marine or terrestrial.
3. They lack setae and each body ring has
several transverse grooves.
1. Over 1,000,000 species are in phylum
Arthropoda; they are highly successful
2. Arthropods have a rigid exoskeleton with
freely movable jointed appendages.
a. The exoskeleton is a strong but flexible
outer covering composed of chitin.
b. Chitin is a strong, flexible, nitrogenous
polysaccharide.
c. It serves as protection, attachment for
muscles, locomotion, and prevention of desiccation.
1. About 40,000 species of crustacea belong to
subphylum Crustacea.
2. Crustaceans are successful and mostly
marine.
3. Head usually bears compound eyes and five
pairs of appendages.
a. First two are antennae and antennules; in
front of the mouth, they have sensory functions.
b. Three pairs (mandibles, first and second
maxillae) lie behind mouth and are used in feeding.
1. Subphylum Uniramia includes millipedes,
centipedes, and insects.
2. Uniramous appendages attached to thorax
and abdomen have only one branch-the leg branch.
3. Head appendages include one pair of
antennae, one pair of mandibles, one or two pairs of
maxillae.
4. Uniramia live on land and breathe by air
tubes called tracheae.
1. Over 900,000 species of insects are in
superclass Insecta; this exceeds all other animal
species combined.
2. Most insects live on land; some are secondarily
aquatic.
3. Insect body is divided into a head, thorax, and
abdomen.
a. Head bears sense organs and mouthparts.
b. Thorax bears three pairs of legs and one or two
pairs of wings; wings provide advantages.
c. Abdomen contains most of the internal organs.
1. Class Chilopoda includes about 2,500
species of centipedes.
a. Body is composed of head and trunk
with many segments; each segment has a pair of
legs.
b. They are carnivorous; the head bears
antennae and mouthparts with jaws.
1. Chelicerates in subphylum Chelicerata include
spiders, scorpions, ticks, mites, horseshoe crabs,
etc.
2. First pair of appendages are chelicerae, second
pair are pedipalps; next four pairs are walking legs.
a. Chelicerae are appendages that function as
feeding organs.
b. Pedipalps are feeding or sensory structures.
3. Appendages attach to a cephalothorax, a
fusion of head and thoracic regions.